PhD, University of Cincinnati, 2023, Engineering and Applied Science: Chemical Engineering

Redox flow batteries (RFBs) are widely considered as a promising option for large-scale electric energy storage especially in renewable power systems. However, deep commercial penetration of RFB storage systems is still limited largely by the lack of low-cost and high-performance ion separators, which are a key RFB component determining the battery efficiency, lifetime, and cost. The existing polymer ion separators have good conductivity and manufacturability but with drawbacks of insufficient ion selectivity and/or inadequate material instability and high-cost. In our recent studies, ion sieve zeolite membranes have been demonstrated with the potential to achieve proton conduction with high rejection of reactive metal ions as well as extraordinary material stability in aqueous RFBs. However, practical realization of the tremendous potential of zeolite membranes as ion separators for RFBs is difficult because the conventional polycrystalline membrane structure presents high resistance from the large thickness and poor manufacturability due to the zeolite film fragility. This dissertation presents a new type of polymer- supported, Nafion-free, 2-dimensional (2D) MFI-type zeolite nanosheet (ZN) layered ultrathin membranes for aqueous RFBs. Fundamental studies have been carried out to establish the methodologies for ZN material and ZN-layered membrane syntheses, reveal the mechanisms of ZN formation, and understand the proton-selective ion transport behavior in the ZN-based membranes. A single crystalline MFI-type ZN-laminated membrane (ZNLM) on porous polyvinylidene fluoride (PVDF) is first evaluated as a RFB ion separator and its performance has been demonstrated to be comparable to the benchmark Nafion117 ® membrane. The PVDF-supported ZNLM (ZNLM-PVDF) exhibits a comparably low are-specific resistance (ASR) but much higher proton-to-vanadyl ion transport selectivity as compared to the Nafion117® membrane of similar total thickness. However, the development of suc (open full item for complete abstract)

Committee: Junhang Dong Ph.D. (Committee Chair); Maobing Tu Ph.D. (Committee Member); Jianbing Jiang Ph.D. (Committee Member); Anastasios Angelopoulos Ph.D. (Committee Member) Subjects: Chemical Engineering

Doctor of Philosophy, University of Akron, 2023, Polymer Engineering

Reliable and sustainable energy is a cornerstone of the modern human's life prosperity. Lately, advancements in portable electronics and smart technologies, along with conventional energy sources rising environmental concerns and shortage threats, had highlighted the cruciality of attaining more sustainable, innovative, and efficient energy harvesting and storage systems. Current overwhelming demand for such energy generating/storing devices is forecasted to boost in the coming years, according to several reports, credited to the projected growth in the utilization of high power and high energy storage systems within modern inventions such as electric vehicles (EV) and autonomous aircrafts. These elements encouraged the exploration of alternative solutions that are derived from clean and renewable natural sources like wind power and solar energy to generate electricity. The enhancement of the current storage systems to achieve great efficiency and high energy storage capacity is another route that enables the development of new technologies. The first part of the dissertation is focused on investigating the electricity generation in multifunctional polymer electrolytes membranes (PEMs) when mechanically deformed, i.e., flexoelectricity originated from the ionic polarization/depolarization principle. Flexural bending of the flexoionic laminates was applied in different modes, intermittent and oscillatory, to study the impact of several parameters on the flexoelectric response and the mechanoelectrical energy conversion efficiency. One of the parameters investigated was the effect of the copolymer network functionality on the mechanoelectric transduction. The impact of the molecular weight of the precursor on the flexoelectric response was also studied. The role of the ionic concentration, i.e., lithium salt loading and multivalent cations salt, on the current and voltage response was systematically explored. The influence of operating temperature on the flexoelect (open full item for complete abstract)

Committee: Thein Kyu (Advisor); Xiong Gong (Committee Chair); Siamak Farhad (Committee Member); Steven S.C. Chuang (Committee Member); Weinan Xu (Committee Member) Subjects: Energy; Engineering; Materials Science; Physical Chemistry; Plastics

Doctor of Philosophy, The Ohio State University, 2022, Chemical Engineering

Developments of green energy alternatives (e.g., ethanol) and advanced CO2 capture technologies play a crucial role in solving the energy and climate crisis. Specifically, membrane-based separation processes provide opportunities as potentially energy-efficient means to extract alcohols or capture CO2. For alcohol extraction, ultrathin-film nanoporous membranes such as zeolite nanosheets may offer large separation factors and high fluxes because of their selective ethanol-to-water adsorption and short diffusion pathway. However, systematic investigations of potential nanosheet candidates are still missing to date, while atomistic understandings of their separation mechanism and structure-property relationship remain limited. For CO2 capture, facilitated transport membranes (FTMs) that utilize reversible chemical reactions between amino groups and CO2 have been demonstrated to offer notably enhanced selectivity and permeance. However, molecular understandings of the reactive diffusion mechanism of CO2 in the FTMs remain limited. This dissertation conducts computational studies to study membrane materials for ethanol separation and CO2 capture. Specifically, in Chapter 2, a screening study of zeolite nanosheets as pervaporation membranes for ethanol separation is discussed to show their separation performance and shed light on the relationship between separation factors, adsorption selectivities, and structural features. In Chapter 3, understandings achieved in the previous chapter are applied to study the alcohol/water pervaporation separation using zeolite membranes with various Si/Al ratios. Key factors identified in Chapter 2, such as surface silanol density and adsorption selectivity, are again shown to play an important role, which rationalizes the separation performance observed experimentally. Aside from zeolite materials, metal-organic frameworks (MOFs) have emerged as a promising class of nanoporous materials as membrane candidates. In order to facilitate (open full item for complete abstract)

Committee: W.S. Winston Ho (Advisor); Nicholas Brunelli (Committee Member); Li-Chiang Lin (Advisor) Subjects: Chemical Engineering

Doctor of Philosophy, Miami University, 2021, Chemistry and Biochemistry

This work is designed to understand how to efficiently synthesize polymers for and to understand two major biotechnology applications - protein-polymer conjugates, and macromolecular surfactants for favorable cell membrane interactions. Polymers are a ubiquitous class of molecules in the world due to the unique and complex properties that arise from combining simple building blocks in particular combinations. Nature has adopted proteins, amino acid polymers that fulfill myriad critical functions. In recent years, the biotechnology industry has begun to manipulate proteins by attaching synthetic polymers to them, conferring invisibility to the immune system for protein drugs, or enhanced stability, activity, or recyclability to enzymes for biocatalysis. A protein molecule on its own is sufficiently complex to require years-long research projects to fully understand. Thus, protein-polymer conjugates are still poorly understood. In this work, we present a technique for the study of conjugates, enabled by reversible deactivation radical polymerization, which by nuclear magnetic resonance allows for an atomic-level view. We also explored the challenge of attaching two distinct polymers to a single protein molecule in an efficient and well-defined manner, which would enable still more complex conjugates. Lipid membranes and the proteins that reside within them are another area of biotechnology that polymers have broken into. Cell membranes and the proteins within them experience a complex play of intermolecular forces. The unique location of membrane proteins makes them difficult to study, as they are not readily crystallized, and resuspension using traditional detergents can be detrimental to protein structure. Styrene-maleic acid copolymers and their relatives are known to form a belt containing lipids and membrane proteins in disk-shaped nanoparticles. These maintain the bilayer shape and avoid the use of detergents and have enabled characterization of previously (open full item for complete abstract)

Committee: Dominik Konkolewicz PhD (Advisor); Richard Page PhD (Advisor); Richard Taylor PhD (Committee Chair); Carole Dabney-Smith PhD (Committee Member); Jason Berberich PhD (Committee Member) Subjects: Biochemistry; Biophysics; Chemistry; Polymer Chemistry; Polymers

Doctor of Philosophy, University of Akron, 2019, Chemical Engineering

The nanofiber material has the potential for multiple applications. In this work, electrospun spring supported tubular nanofiber membrane and their applications has been studied. One application is hydrogenation of phenol to cyclohexanone through nanofiber supported catalyst. The electrospun nanofiber supported catalytic membranes were tested to evaluate conversion and selectivity of hydrogenation of phenol. The feasibility of using the membranes as catalyst support and the reaction kinetics of prototype tubular membrane reactor were determined. A second application of the electrospun membrane is to separate the dispersion of water drops in Ultra Low Sulfur Diesel (ULSD). The novel flow through reactor was designed which has a small diameter. The catalytic electrospun fiber membrane was applied in this reactor for phenol hydrogenation reaction. A high reaction conversion and selectivity were achieved. Two polymer materials with hydrophobic and hydrophilic properties were selected. For both phenol hydrogenation reaction and filtration experiments, how the mixture of hydrophobic and hydrophilic electrospun membranes affect the performance was experimentally tested.

Committee: George Chase (Advisor); Zhenmeng Peng (Committee Member); Jie Zheng (Committee Member); Toshikazu Miyoshi (Committee Member); Hamid Bahram (Committee Member) Subjects: Chemical Engineering; Materials Science; Polymers

Doctor of Philosophy, The Ohio State University, 2019, Mechanical Engineering

Lithium-ion batteries (LIBs), during high duty cycles, generate heat which can lead to rapid and uncontrolled exothermic reactions known as thermal runaway, causing fires and explosions. The goal of this dissertation is to develop a smart membrane separator (SMS) for the reversible shutdown of LIBs to prevent thermal runaway. In this work, it is demonstrated that the conducting polymer polypyrrole doped with dodecylbenzenesulfonate (PPy(DBS)) will provide the necessary properties for the SMS based on its controlled ion transport properties. PPy(DBS), in the oxidized state, is electroneutral and does not interact with ions in solution. During reduction, the bulky, immobile DBS- dopants become excess negative charges in the polymer backbone and act as redox sites for cation ingress to maintain electroneutrality. It is therefore expected no ion movement across the polymer will occur in its oxidized state, and the immobile DBS dopants will serve as hopping sites for cation movement across the polymer in its reduced state. This research has led to the development of a SMS for enhanced performance of LIBs and their reversible shutdown for thermal runaway prevention. The following original contributions have resulted from this work: (1) The fabrication of an ionic redox transistor (IRT) as an electrochemical device that regulates ion transport through its bulk as a function of its redox state. This IRT consists of PPy(DBS) electropolymerized onto and spanning the pores of a thin, porous substrate. (2) A mechanistic interpretation for ion transport across PPy(DBS) polymer bulk. A geometric representation of redox sites is used to define ionic filaments for ion turnover. (3) The development of a model for reversible switching of ion charge type transport across PPy(DBS) in lithium salt containing organic solvents with low DBS- salt dissociation constants. A continuous spectrum for the balance of intrinsic binding energy of LiDBS ionic couples, electrochemica (open full item for complete abstract)

Committee: Vishnu Baba Sundaresan (Advisor); Marcello Canova (Committee Member); Jung Hyun Kim (Committee Member) Subjects: Mechanical Engineering

Doctor of Philosophy, University of Akron, 2018, Polymer Engineering

Some living cells are known to generate bioelectricity by manipulating the ion concentration gradient across the cell membrane via passive and active ion transports, which are controlled by ion gates and pumps. This process involves polarization and depolarization of the cell membrane, resulting in electrical potential often called membrane potential. Neuron cells utilize such ionic polarization process to send electrical signals for communication and control of body parts. On the other hand, electroplaques in electric eels can store sizable electrical energy and release it on demand for defending and hunting. A similar ionic polarization potential can be generated via bending deformation (as a means of exerting a pressure (stress) gradient) of polymer electrolyte membrane (PEM), which was originally developed as ion conducting solid medium for solid-state Li-ion batteries. This is the motivation of the present dissertation to explore the novel flexoelectric effect in the aforementioned solid-state PEM by subjecting it to mechanical deformation. A plausible mechanism has been proposed to explain the mechano-electrical transduction in the above solid PEMs, wherein ionic polarization occurred as a result of ion diffusion under pressure (stress) gradient. The flexoelectric coefficient has been measured to be as high as ~300 µC/m, which is several orders of magnitude higher relative to those of other flexoelectric materials hitherto reported in literature. These new and fascinating features found in the present solid PEM system open up a new avenue of polymeric energy materials for diverse applications such as flexible sensor and energy harvesting devices.

Committee: Thein Kyu (Advisor) Subjects: Energy; Engineering; Materials Science; Polymer Chemistry; Polymers

Bachelor of Science, Walsh University, 2018, Honors

An active biomass carbon catalyst support was synthesized with the potential to enhance the activity of the platinum catalyst in PEM fuel cells. Garbanzo beans, an inexpensive source of nitrogen dense carbon, were used to produce the biomass carbon catalyst support, biosupport. The biosupport was synthesized by means of pyrolysis in the absence of oxygen in order to maximize nitrogen retention. To characterize the prepared biosupport, cyclic voltammetry experiments were conducted on the biosupport and a standard carbon support, Vulcan XC 72, by scanning the potential from -270 mV to 950 mV in both perchloric and sulfuric acid. The resulting cyclic voltammograms of the biosupport had a cathodic peak at 750 mV and an anodic peak at 220 mV whereas the Vulcan XC 72 had no significant peaks which is characteristic of an electrode in which no electrochemical activity is occurring. The peaks present on the cyclic voltammogram of the biosupport indicated a reversible oxidation and reduction processes taking place. The intensity of the cyclic voltammogram peaks, indicating reversible oxidation and reduction reactions for the biosupport, was greater in the perchloric acid, which indicates that the biosupport is more active, in regards to electrochemical reactions, in the perchloric acid. Cyclic voltammetry scans of synthesized 20% w/w platinum on the biosupport, by means of homogenous deposition using NaBH4, showed compromised durability from a large decrease in the intensity of the hydrogen adsorption peak at 100 mV in perchloric acid after two rounds of scans. The durability of the synthesized 20% w/w platinum on the biosupport was less compromised in sulfuric acid, with significantly less decrease in the hydrogen adsorption peak at 100 mV. These results presented evidence for a negative correlation between the extent of the activity and durability of the biosupport.

Committee: Peter Tandler Ph. D. (Advisor) Subjects: Chemistry

Master of Science, University of Akron, 2017, Polymer Engineering

To investigate physical and electrochemical properties of polymer electrolyte membranes (PEMs) containing various dinitriles such as succinonitrile (SCN), glutaronitrile (GLN) and adiponitrile (ADN), binary and ternary phase diagrams of poly(ethylene glycol) diacrylate (PEGDA), GLN and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) blends were firstly established in this thesis. The binary phase diagram of PEGDA/GLN system was self-consistently solved based on the combined free energies of Flory-Huggins theory for liquid-liquid demixing and phase field theory for crystal solidification. Computed liquidus and solidus lines were compared with crystal melting temperatures of the binary pairs, obtained by differential scanning calorimetry (DSC) measurement. The binary phase diagram of LiTFSI/GLN system was drawn according to crystal melting temperatures of the binary pairs determined by DSC measurement. Then coexistence regions of each binary phase diagram were verified by polarized optical microscopy. Subsequently, the ternary phase diagram of PEGDA/GLN/LiTFSI at 25 oC were established. Guided by isotropic regions within ternary phase diagrams established in this thesis and previous studies, polymer electrolyte membranes (PEMs) plasticized by various dinitriles thus fabricated via photo-polymerization afforded transparent, homogeneous films. The ionic conductivity of these PEMs was determined by AC impendence spectrometer, which showed high ionic conductivity up to 10-3 S/cm at room temperature. Of particular interest is that GLN-PEM reveals the highest ion conductivity among the three PEMs tested. To analyze the electrochemical performance of PEMs used in lithium-ion batteries, SCN-PEM, GLN-PEM, and ADN-PEM were assembled into Li4Ti5O12/PEM/Li and LiFePO4/PEM/Li half-cells. The half-cell containing GLN-PEM exhibits the best charge-discharge cycling performance, which is consistent with the highest ionic conductivity of the GLN plasticized PEM.

Committee: Thein Kyu (Advisor); Xiong Gong (Committee Chair); Zhenmeng Peng (Committee Member) Subjects: Engineering; Polymers

Master of Science in Polymer Engineering, University of Akron, 2017, Polymer Engineering

Based on the ternary phase diagram of polyethylene (glycol) diacrylate (PEGDA), ethylene carbonate (EC) and lithium bis-(trifluoromethane sulfonyl) imide (LiTFSI), polymer electrolyte membranes (PEMs) were fabricated in various proportions via photo-polymerization. Ionic conductivities of PEMs containing various ratios of three constitutes were measured by means of AC Impedance spectroscopy. Solid polymer electrolyte membrane, consisting of 20/40/40 PEGDA/EC/LiTFSI, was chosen as the appropriate solid PEM that afforded high ionic conductivity and good mechanical properties. The ionic conductivity of such PEM at 25 °C was found to reach a superionic level of 10-3 S cm-1, which is rather difficult to come by for a conventional solid-state electrolyte. More importantly, the present PEM was compatible with conventional electrodes such as LiFePO4 (LFP), Li4Ti5O12 (LTO) and graphite. The Li/PEM/LTO cell was found to achieve the capacity value of 180 mAh/g at a current rate of 0.2 C for both room temperature and 60 °C, which was even higher than the theoretical capacity of LTO of 170 mAh/g. What is more, the capacity of Li/PEM/LTO cell at 2 C, which was rather a high speed for a solid electrolyte membrane, could reach 140 mAh/g, indicating that the PEM was truly compatible with LTO electrode at both high cycling speed and high temperature. In addition, the LTO half-cell was found to survive charge/discharge cycling for more than 200 cycles with 95% retention, which implied that little or no degradation of the electrode occurred during the charge/discharge cycling. The Li/PEM/LFP half-cell and Li/PEM/graphite half-cell also reached the capacity close to the theoretical value. The high thermal and chemical stability of PEM confirmed that the present solid PEM could be a great alternative to the liquid electrolyte having advantages of non-flammable, solvent free, flexible, light weight, low cost and easy processing.

Committee: Thein Kyu (Advisor); Xiong Gong (Committee Member); Zhenmeng Peng (Committee Member) Subjects: Polymer Chemistry; Polymers

Doctor of Philosophy, The Ohio State University, 2015, Chemical Engineering

Polymer membrane is a cost-effective and energy-efficient approach for separation and fuel cell applications. In this research, two types of polymer membranes were synthesized for different applications. The first type is CO2-selective membranes for carbon capture from flue gas, and the second type is hydroxide-exchange membranes for alkaline fuel cell application. CO2 separation from flue gas streams is one of the most important solutions to greenhouse gas driven climate change. In this research, two types of CO2-selective polymer membranes were synthesized: (1) ethylene oxide (EO)-based membranes and (2) amine-based membranes. The former is based on the solution-diffusion transport mechanism, while the latter is based on the facilitated transport mechanism. For the membranes containing EO groups, membranes were synthesized with polyamide-polyethyleneoxide (PA-PEO) copolymer blended with poly(ethylene glycol) dimethyl ether (PEG-DME) or polyethylene glycol (PEG). For the membranes containing amino groups, a high-molecular-weight polyamine was successfully synthesized. Selected aminoacid salts were incorporated into the polyamine solution for membrane preparation. The polyamine served as the fixed-site carrier, whereas the aminoacid salts acted as mobile carriers. Both types of membrane have shown promising results for CO2/N2 separation from flue gas. Alkaline fuel cells (AFC) has received increasing attention nowadays because they enable non-precious metals to replace the platinum as the catalyst, and they have the potential to offer fuel flexibility, reduce fuel crossover and prevent carbonate precipitation. Current research about alkaline fuel cell membranes mostly focused on quaternary ammonium-based polymer membranes. However, these membranes have shown low ionic conductivity and, poor chemical and thermal stability. Ionic liquids are organic molten electrolytes which have ideal conductivity, excellent thermal and chemical st (open full item for complete abstract)

Committee: W.S. Winston Ho (Advisor); Stuart Cooper (Committee Member); Nicholas Brunelli (Committee Member) Subjects: Chemical Engineering

Master of Science, University of Akron, 2015, Physics

Cellular membranes are complex assemblies and a clear understanding of the physical interactions during their function is of paramount importance. Here, we perform two separate studies for a better understanding of the interactions between membrane compartments and other biomolecules. In the first study, we developed a coupler to integrate a high sensitivity spectrometer with an epi-fluorescence microscope to measure fluorescence spectra of small area samples (400 micrometer squared). We applied our measurements on standard samples, performed three corrections on them and after a linear demixing process, the percentage of FRET efficiency was obtained. The development of this method will be advantageous in future single cell studies for detecting population heterogeneity. In the second study, we investigated the dynamics of membrane lipids in a supported lipid bilayer. Single particle tracking total internal reflection fluorescence microscopy (TIRF) was used to study the lateral mobility of phosphatidylinositol phosphate (PIP) lipids with and without an adsorbed polycationic polymer, quaternized polyvinylpyridine (QPVP). Diffusion coefficients were determined with Brownian and anomalous models. Our results indicate a decrease in diffusion coefficient of the lipids in the presence of QPVP in comparison to its absence, revealing their interaction.

Committee: Adam Smith (Advisor); Jutta Luettmer-Strathmann (Committee Chair); Sergei Lyuksyutov (Committee Member) Subjects: Biophysics; Chemistry; Physical Chemistry; Physics

PhD, University of Cincinnati, 2014, Engineering and Applied Science: Chemical Engineering

Polymers containing perfluorosulfonic acid (PSA) groups have been used as solid acid catalysts for many years. These materials have unique and extensively studied hetero-phase morphology of hydrophilic PSA domains dispersed within a hydrophobic hydrocarbon matrix. However, the correlation between the intrinsic activity of the PSA domains and changes in solid-state morphology remains uncertain. This dissertation investigates the immobilization of suitable organic molecules within the PSA hydrophilic domains from the gas and liquid phases and by means of acid catalyzed reaction that forms a colored product. This approach permits direct comparisons of immobilization site to active site to PSA group concentration and how changes in membrane morphology influence the kinetics and thermodynamics of the solid-state reaction process. The approach is also shown to produce sensing elements for the portable, real-time detection and measurement of highly toxic trimellitic anhydride (TMA) vapors.

Committee: Anastasios Angelopoulos Ph.D. (Committee Chair); Jonathan Bernstein M.D. (Committee Member); Junhang Dong Ph.D. (Committee Member); Stephen Thiel Ph.D. (Committee Member) Subjects: Chemical Engineering

Master of Science (MS), Wright State University, 2014, Chemistry

A series of fluorinated poly(arylene ether)s, PAE, bearing sulfonated pendent sulfonyl groups, was prepared. A range of Ion Exchange Capacity (IEC) values were achieved by varying the ratios of sulfonated and non sulfonated monomers. Incorporation of both of the monomers was confirmed by NMR spectroscopy and characterization of the thermal properties was done using thermogravimetric analysis (TGA) and differential scanning (DSC). Polymers with these IEC values were synthesized in order to explore their use as a potential alternatives to the widely studied proton exchange membrane, Nafion, with an IEC of 0.91 meq/g. Using N-phenyl-3,5-difluorobenzene sulfonamide as the starting material a series of N-alkyl derivatives, with chain lengths of 3 to 12 carbon atoms, was prepared and characterized followed by conversion to the corresponding PAE. The polymer structure was confirmed by 1H and 13C NMR spectroscopy. Molecular weight data were obtained by size exclusion chromatography (SEC) and thermal data were acquired using TGA and DSC. The effect of alkyl chain length on the thermal stability and glass transition temperatures, Tg, values was determined. Increasing the alkyl chain length led to a decrease in the Tg values, which ranged from 111 down to 46 oC.

Committee: Eric Fossum Ph.D. (Advisor); William Feld Ph.D. (Committee Member); Daniel Ketcha Ph.D. (Committee Member) Subjects: Chemistry

Doctor of Philosophy, University of Akron, 2014, Polymer Science

Porous materials comprising polymeric and inorganic segments have attracted interest from the scientific community due to their unique properties and functionalities. The physical and chemical characteristics of these materials can be effectively exploited for adsorption applications. This dissertation covers the experimental techniques for fabrication of poly(vinyl alcohol) (PVA) and silica (SiO2) porous supports, and their functionalization with polyamines for developing adsorbents with potential applications in separation of CO2 and catalysis of organic reactions. The supports were synthesized by processes involving (i) covalent cross-linking of PVA, (ii) hydrolysis and poly-condensation of silica precursors (i,e,. sol-gel synthesis), and formation of porous structures via (iii) direct templating and (iv) phase inversion techniques. Their physical structure was controlled by the proper combination of the preparation procedures, which resulted in micro-structured porous materials in the form of micro-particles, membranes, and pellets. Their adsorption characteristics were tailored by functionalization with polyethyleneimine (PEI), and their physicochemical properties were characterized by vibrational spectroscopy (FTIR, UV-vis), microscopy (SEM), calorimetry (TGA, DSC), and adsorption techniques (BET, step-switch adsorption). Spectroscopic investigations of the interfacial cross-linking reactions of PEI and PVA with glutaraldehyde (GA) revealed that PEI catalyzes the cross-linking reactions of PVA in absence of external acid catalysts. In-situ IR spectroscopy coupled with a focal plane array (FPA) image detector allowed the characterization of a gradient interface on a PEI/PVA composite membrane and the investigation of the cross-linking reactions as a function of time and position. The results served as a basis to postulate possible intermediates, and propose the reaction mechanisms. The formulation of amine-functionalized CO2 capture sorbents was ba (open full item for complete abstract)

Committee: Steven Chuang Dr. (Advisor); Matthew Becker Dr. (Committee Member); Mesfin Tsige Dr. (Committee Member); Darrell Reneker Dr. (Committee Member); Jie Zheng Dr. (Committee Member) Subjects: Chemical Engineering; Chemistry; Climate Change; Energy; Engineering; Environmental Engineering; Experiments; Fluid Dynamics; Materials Science; Molecules; Nanotechnology; Organic Chemistry; Polymer Chemistry; Polymers; Scientific Imaging; Technology

Doctor of Philosophy, University of Akron, 2013, Chemical Engineering

This dissertation encompasses the doctoral work of the author, which focused on the ideation and materials synthesis of novel sensor technologies for biomedical and environmental applications. The purpose of this work is to identify and exploit the nanostructured properties of certain materials to produce advanced sensing platforms, utilizing the advances made by nanotechnology. Herein, a number of developed sensors are described using electrochemical and colorimetric transduction techniques. A number of background chapters providing an introduction to nanomaterials, typical sensor fabrication routes, and sensor technologies are provided, followed by experimental studies of the developed sensors. The author describes a polymer/multi-walled carbon nanotube sensing platform, which has been found to be both selective and sensitive to sodium ions at normal physiological range. Two chapters describing experimental work related to both a colorimetric water contaminant preconcentration/detection system—able to detect contaminants at the United States Environmental Protection Agency maximum contaminant level—and an electrochemical water contaminant detection system are discussed. A chapter describing the theoretical and optimization modeling of the polymer/multi-walled carbon nanotube sensing platform is also enclosed. Through this work, the author has developed a number of novel sensing technologies for both biomedical and environmental applications.

Committee: Chelsea Monty Dr. (Advisor); Lu-Kwang Ju Dr. (Committee Member); George Chase Dr. (Committee Member); Gang Cheng Dr. (Committee Member); Marnie Saunders Dr. (Committee Member); Wiley Youngs Dr. (Committee Member) Subjects: Analytical Chemistry; Biomedical Engineering; Chemical Engineering; Environmental Engineering

Doctor of Philosophy, The Ohio State University, 2013, Chemical and Biomolecular Engineering

CO2 capture from fuel and flue gases is critical to reducing the anthropogenic influence on climate change. Solvent absorption-, adsorption- and membrane-based processes have been widely studied for this application. Compared to the former two alternatives which are equilibrium-based, membrane separation is rate-based and does not involve phase change. Membranes hold great promise for CO2 capture due to their potentially lower energy consumption compared to other processes, operational simplicity with no handling of steam and condensed phases, lower water consumption, compactness, and ease of maintenance due to absence of moving parts. CO2 (H2S)-selective membranes with appropriate separation capabilities can be used to separate CO2 from waste gases in a fossil fuel-based power plant or both CO2 and H2S from syngas streams containing hydrogen. They can also be integrated with water gas shift (WGS) reaction for effective CO, CO2 and H2S clean up. In the context of hydrogen purification for fuel cells, a detailed 2-D model incorporating mass, energy and pressure drop equations for describing the transport in an intricate spiral-wound WGS membrane reactor was developed and validated using prior experimental data. Such a configuration is also used in state-of-the-art water purification processes and was the preferred choice for the advanced gas separation membranes studied in this work. A simplified 1-D version of the same model was then combined with a detailed cost methodology to study the feasibility of membrane processes for post-combustion CO2 capture (PCC) in a coal-based power plant. From this study, valuable insights into the membrane properties required to meet the economic goals of PCC were gained. As a part of the experimental work, we first scaled up an existing amine-based facilitated transport membrane to purify hydrogen for fuel cells. The membranes were then characterized for their separation performance using a gas permeation set-up and compared w (open full item for complete abstract)

Committee: W.S. Winston Ho PhD (Advisor); Stuart Cooper PhD (Committee Member); David Tomasko PhD (Committee Member) Subjects: Chemical Engineering

PhD, University of Cincinnati, 2002, Engineering : Materials Science

This work was focused on the investigation of charge and discharge properties of polypyrrole/polyimide (PPy/PI) composites. Capacitive and accumulative properties of PPy/PI composites were studied in details targeting application of the composite in polymer based charge storage devices: supercapacitors and polymer batteries. Polyimide was chosen as a matrix because of its excellent mechanical properties and electroactivity. Composites were prepared electrochemically on stainless steel, and studied by potential step amperometry and electrochemical impedance spectroscopy. The composition of the composite was studied by FTIR. Mechanism for PAAc conversion to PI was studied by FTIR ands DSC. Morphology was determined by SEM. Doping-dedoping of PPy in the composite in competition with doping-dedoping of PI along with formation of double electric layers were found to be responsible for a difference between discharge behaviors of PPy and PPy/PI composite. Charge storage ability was greatly affected by PPy. PPy along with factor of preconversion of poly(amic acid) (PAAc) matrix to PI was found to play a key role in charge storage properties of PPy/PI composite. DC polarization was found to alter the supercapacitance of the composite. Two mechanisms: orientation polarization and ion jump polarization were suggested to be responsible for supercapacitance in double electric layer. PPy/PI composite can be considered as a promising material for use in supercapacitors as a material for active polymer electrodes in polymer batteries. Additional advantage of use of PPy as a filler for PI matrix is the reduction of activation energy to conversion to polyimide. This was shown by differential scanning calorimetry and FTIR. Activation energy of the reaction of imidization can be reduced significantly by the presence of PPy.

Committee: Dr. Jude O. Iroh (Advisor) Subjects:

Doctor of Philosophy in Engineering, University of Toledo, 2010, Chemical Engineering

Although commercially available cellulose acetate membranes are characterized by having high fluxes during filtration as compared to other membrane materials, they are more prone to microbial attack and organic fouling because of their natural cellulose acetate backbone structures. Fouling, or the accumulation of foreign substances on the membrane surface, occurs mostly due to hydrophobic interactions between the membrane and the foreign substances, especially natural organic matter (NOM). In order to reduce the hydrophobic interactions and thereby fouling due to NOM, flexible hydrophilic poly(ethylene glycol) (PEG) monomer chains were grafted to the cellulose acetate membrane to increase its hydrophilicity. Two methods were used to achieve PEG grafting on the membrane surface. In Method I, grafting was achieved by the action of an oxidizing agent for free radical development, followed by monomer for polymerization, and a chain transfer agent (CTA) for termination of the polymerization. Two different techniques of introducing the chemicals to the membrane were investigated. These were a bulk approach, where membranes were immersed in the chemical solutions, and drop approach, where chemicals were added drop wise to the surface of the membrane to avoid polymerization within the pores. Both techniques led to improvements in membrane performance, as observed by lower fouling, lower flux declines and lower rates of flux decline, when compared to unmodified membranes. While the drop approach displayed slightly higher initial flux values, the bulk method was preferred for its ease of modification and replication. Method II was characterized by a greener solvent-free enzymatic polycondensation to graft PEG to the membrane surface. NOM feed solutions were used to compare organic fouling between the modified and unmodified membranes. Modification led to higher fluxes, lower flux declines, and a more reversible fouling layer easily removed by backwashing during operation. Met (open full item for complete abstract)

Committee: Isabel Escobar PhD (Advisor); Sasidhar Varanasi PhD (Committee Member); Maria Coleman PhD (Committee Member); Dong-Shik Kim PhD (Committee Member); Jared Anderson PhD (Committee Member) Subjects: Chemical Engineering; Chemistry; Engineering; Environmental Engineering

Doctor of Philosophy, The Ohio State University, 2012, Mechanical Engineering

The primary objective of this study is to develop a multi-scale computational fluid dynamics (CFD) model to predict the performance of a polymer electrolyte membrane fuel cell (PEMFC). In particular, two critical factors affecting PEMFC performance, namely water and current transport through the polymer electrolyte membrane, and the effect of the cathode catalyst layer structure and composition are examined in detail. The implementation of phenomenological membrane models within CFD codes requires coupling of the conservation equation for the so-called water content within the membrane to the conservation equations for species mass outside the membrane. The first part of this dissertation investigates the accuracy and efficiency of various strategies for implementing phenomenological membrane models within the framework of a CFD code for prediction of the overall PEMFC performance. First, three popular phenomenological membrane models are investigated, and the accuracy of each model is assessed by comparing predicted results against experimental data. Results indicate that the Springer model and the Nguyen and White model over-predict the drying of the membrane, while the Fuller and Newman model provides the best match with experimental data. Following these studies, three strategies for implementation of the membrane model are investigated: (1) two-dimensional (2D) transport of water and current in membrane, (2) one-dimensional (1D) transport and (3) 1D transport with approximate transport properties. Fuller and Newman's membrane model is used for these studies. The results obtained using the three approaches are found to be within 4% of each other, while there is no significant difference in the computational time required by the three strategies, indicating that an analytical 1D transport model for the membrane that uses approximate properties is adequate for describing transport through it. In the second part of the dissertation, the effect of the cathode cataly (open full item for complete abstract)

Committee: Sandip Mazumder (Advisor); A Terrence Conlisk Jr (Committee Member); Yann Guezennec (Committee Member); Vishwanath Subramaniam (Committee Member) Subjects: Chemical Engineering; Energy; Engineering; Mechanical Engineering